weidong3630 commented on a change in pull request #1338: [CALCITE-3210] Fix the
bug that RelToSqlConverter converts "cast(null as $type)" just as null
URL: https://github.com/apache/calcite/pull/1338#discussion_r308111279
##########
File path:
core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java
##########
@@ -195,15 +198,57 @@ public Result visit(Project e) {
final Builder builder =
x.builder(e, Clause.SELECT);
final List<SqlNode> selectList = new ArrayList<>();
+
+ boolean checkNull = isNeedCastNull(stack);
for (RexNode ref : e.getChildExps()) {
SqlNode sqlExpr = builder.context.toSql(null, ref);
+ if (checkNull && SqlUtil.isNullLiteral(sqlExpr, false)) {
+ sqlExpr = castNullType(sqlExpr,
e.getRowType().getFieldList().get(selectList.size()));
+ }
addSelect(selectList, sqlExpr, e.getRowType());
}
builder.setSelect(new SqlNodeList(selectList, POS));
return builder.result();
}
+ /**
+ * Check whether null item in select need to be casted
+ * @param stack stack of visit
+ * @return If null need to be casted then return true, otherwise return
false.
+ */
+ private static boolean isNeedCastNull(Deque<Frame> stack) {
+ final int stackSize = stack.size();
+ if (stackSize > 1) {
+ int i = 1;
+ for (; i < stackSize; i++) {
+ RelNode currentNode = Iterables.get(stack, i).r;
+ if (!(currentNode instanceof SingleRel)) {
+ break;
+ } else if (currentNode instanceof Project) {
+ //direct or indirect input of Project need to cast null type
+ break;
+ } else if (currentNode instanceof TableModify) {
+ //direct or indirect input of TableModify do not need to cast null
type
+ return false;
+ }
+ }
+ }
+
+ return true;
+ }
+
+ /**
+ * cast null with type
+ * @param sqlNodeNull null SqlNode
+ * @param field field description of sqlNodeNull
+ * @return SqlNode with cast to type.
+ */
+ private SqlNode castNullType(SqlNode sqlNodeNull, RelDataTypeField field) {
Review comment:
Thanks, I will fix it.
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